According to Kantar, the UK's leading supermarkets are also under growing pressure from the discounters Aldi and Lidl, and Waitrose, the upmarket supermarket.

For the first time on record, the "big four" supermarkets - Tesco, Asda, Sainsbury's and Morrisons - are all losing market share in the UK.

James Anstead, analyst at Barclays, said that Tesco is likely to report a 1.8pc drop in like-for-like sales for the third quarter, compared to flat sales in the previous three months.

He said: "It seems unlikely that Tesco’s Q3 trading statement will be the turning point that the market is looking for.

"The Kantar data suggests that much of the slowdown is due to weaker market growth – and the most recent set of data looked much more encouraging for Tesco. However, it faces tougher comps in the upcoming two months from last year’s successful Christmas period."

Analysts at Deutsche Bank have forecast a 1.5pc drop in UK like-for-likes, adding: "While the backdrop in the UK is clearly very tough and we forecast a Q3 lfl sales decline of 1.5pc we expect a relatively reassuring message on UK margins, reflecting a broadly stable market share performance versus the rest of the big four."